1. Field
The present embodiments relate to techniques for controlling a brushless DC motor. More specifically, the present embodiments relate to techniques for generating a coil switching signal for a brushless DC motor.
2. Related Art
Typically, in order to drive the stator coils of a brushless DC motor, the magnitude and polarity of the magnetic field of the rotor is detected with a sensor. As the rotor rotates, the magnetic field of the rotor at a stator coil switches polarity. The sensor detects this polarity switch and a motor controller then generates a signal to reverse the polarity of the magnetic field generated by the stator coil. However, for some motor controllers, the threshold magnetic field at which the motor controller generates the signal to reverse the direction of the stator coil current is set so that the coil current switches only after the polarity of the magnetic field of the rotor has switched. Then, for the portion of the cycle in which the polarity of the magnetic field of the coil is the same as the polarity of the magnetic field of the rotor, the motor will act like a generator and back emf may cause the tail end of the coil driver current to peak. This peaking of the driver current may cause undesirable noise, and may decrease the efficiency of the motor.
Hence, use of brushless DC motors may be facilitated by improved techniques for generating a coil switching signal.